Calculating the Design Life Cycle of Pressure Vessels

The 4 big time-dependant failure mechanisms are:

Corrosion -

• Determine an industry standard corrosion allowance from data provided by NACE and apply simple multiplication/division. For example, let's say that NACE specifies an average corrosion rate of 0.005" per year; for a design life of 25 years, you would require a minimum of 0.125". (of course this all gets thrown out the window if the vessel is operated outside of normal conditions or the user decides to perfrom an acid wash with hydroflouric acid during a shutdown)

Fatigue -

• The parameters must be provided by the user, for example, how many anticipated start-ups and shut-downs, or how many batch pressurizations will be conducted on the vessel per year. Then perform fatigue analysis as per the design code.

Creep -

• Relate design temperature to material stresses and see if they are in the time-dependant stress allowables in the design code. Apply fundamental creep analysis, for example, by using the ASM Specialty Handbook.

High Temperature Hydrogen Attack

• Review API 941 to determine susceptiblity.
  

You better be careful how you word the final answer. There is no way that anyone can estimate the life cycle of equipment such as that, there are too many variables. We have been asked the same question many times and then have been asked to guarantee it with a financial deposit.

Our standard answer is that we will and have used the best known engineering practices in the industry. And we would be happy to beef up the design for XXX $ USD.